Emerson Surge and Signal Protection manual Multi-Stage System of Suppression

Multi-Stage System of Suppression

S•A•D Hybrid Technology

The Liebert Hybrid Advantage is the first hybrid product in the industry to offer a true, coordinated multi-stage system of suppression. It integrates the fast response time of the Silicone Avalanche Diode (SAD) with the high-energy capability of the standard Liebert Interceptor MOV (Metal Oxide Varistor). Its patent-pending Surge Current Transition Circuit continually monitors the operating level of the SAD-switching to the secondary network of MOVs long before component failure becomes a concern.

Other "hybrid" products fall into one of two categories:

Self-sacrificing:This system significantly degrades or fails with nominal fluctuations or high-energy events. This design is extremely inconvenient to the customer, and more importantly, it leaves an opportunity for critical load upsets/failures.

Oversized components: Large components allow the system to deal with nominal line voltage, as a result clamping levels increase, defeating what it is designed to do.

Typical Hybrid Advantage Surge Current Sharing Data

Hybrid SAD Module Interceptor MOV Module

	100.0
	90.0
(%)	80.0
Current	70.0
	60.0
Surge
	50.0
of
Percentage	40.0
	30.0
	20.0
	10.0
	0.0
	0	5,000	10,000	15,000	20,000	25,000	30,000

Total Surge Current (Amperes)

The Liebert Answer:

The transitional method

Our answer lies in a two-part design that actively disconnects the nominally close components during a sustained overvoltage and transitions from a sensitive SAD circuit to a hardier MOV array when subjected to damaging transient levels.

First, a solid state comparator network actively switches the SAD components out of the transient control circuit when exposed to line voltages in excess of their Maximum Continuous Operating Voltage (MCOV). While SAD components are removed from the system, an appropriately sized transient control network is available for continued protection. During this disconnect phase, the nominal levels are continually monitored until the system voltage is stable, at which point the SAD circuit is brought back on line.

Second, a regulated amount of high- energy surge current is transitioned to the secondary MOV suppression modules. This is accomplished through an impedance matching network utilizing a series of controlled copper geometries in conjunction with custom engineered high-voltage/high-energy component distribution. This ultimately limits the amount of high-energy surge current through the SAD module to an acceptable level and diverting the remaining surge current through the MOV module.

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